The 1957 Pacific hurricane season was a moderately active year in which 13 tropical cyclones formed. The hurricane season ran through the summer and fall months which conventionally delimit the period during which most tropical cyclones form in the northeastern Pacific Ocean. The first tropical cyclone developed on July 15. The final storm dissipated on December 6, becoming one of the few Pacific storms to exist outside of the seasonal dates. Of the season's 13 storms, five of these formed or crossed into the central Pacific.
During the season, five storms impacted land. Hurricane Twelve was the deadliest, leaving eight casualties in Mazatlán and the costliest was Hurricane Nina, causing an estimated $100,000 in losses. In addition to the damage, four people were killed by Nina in Hawaii. Hurricane Six killed seven people and Hurricane Ten killed two in Mexico.
Systems
Hurricane Kanoa
The first hurricane of the season was identified by the National Weather Bureau in San Francisco, California on July 15. The previous day, the S.S. Garvel Park recorded sustained winds of when it was situated roughly south of Manzanillo, Mexico. Although listed as a Category 1 hurricane for its entire known existence by the hurricane database, the storm was not confirmed to have attained hurricane intensity until July 21. The storm took a steady westward track during the early portion of its existence in response to a strong ridge located north of Hawaii. On July 18, the National Weather Bureau discontinued advisories on the storm as no information on it was being received.
On July 21, a vessel named Cape Horn relayed information regarding the storm to the National Weather Bureau, leading to them re-issuing advisories on the storm, upgrading it to a hurricane. The following day, a reconnaissance mission from Oahu, Hawaii located the storm's wide eye and recorded sustained winds of and gusts up to . Shortly after, the storm likely attained its peak intensity as a high-end Category 1 hurricane, with winds of . Early on July 23, warning responsibility of the storm was given to the National Weather Bureau in Honolulu, Hawaii.
Upon transferring responsibility, the hurricane was given the name Kanoa, the Hawaiian name meaning "the free one". As the storm approached Hawaii, it began to weaken as convection filled the eye. The storm's track mirrored that of the shipping lane between the Panama Canal and Hawaii, leading to several ships being affected. Colder air also began to enter the circulation, leading to further weakening. By the time the system reached Hawaii, it was no more than an area of disturbed weather. The remnants of Kanoa persisted until July 26, at which time they dissipated over the Hawaiian Islands. The remnants of the storm brought beneficial rainfall to most of Hawaii, with heavy rains being reported in parts of the Big Island.
Hurricane Two
Roughly two weeks after Kanoa dissipated, the season's second hurricane was identified over the open waters of the eastern Pacific on August 6. This storm traveled in a similar fashion to Kanoa in response to a high-pressure system over the northern Pacific. By August 9, the system turned northwest and weakened. Cold, dry air began to enter the storm as it accelerated over cooler waters. Several reconnaissance missions were flown into the storm due to rapid changes in the storm's wind field and structure. Late on August 10, the system intensified into a Category 1 hurricane and its forward motion slowed as it turned more westward.
Although at an unusual latitude, the storm maintained this intensity for over a day before weakening to a tropical storm. During the afternoon of August 13, the small system re-intensified into a hurricane. Reconnaissance reported that gale-force winds extended no more than from the storm's eye. Shortly thereafter, the system further intensified into a Category 2 hurricane, attaining maximum winds of . Weather maps at the time depicted the storm as having a minimum pressure of 987 mbar (hPa). By August 14, the storm began to weaken once more, gradually becoming a tropical storm on August 15. After turning northward, the cyclone became extratropical at a high latitude of 39.8°N.